(1) Technical Field
The subject invention relates to a vertical rotary indirect screen printer used for printing images on objects which are sequentially cycled past the printer.
(2) Description Of The Prior Art
The subject invention relates to a vertical rotary indirect screen printer used for printing images on objects which are sequentially cycled past the printer. More specifically, the subject invention is directed toward a rotary indirect screen printer used for printing cylindrical objects such as spark plug insulators or the like.
Indirect printing assemblies are old in the art and a number of apparatuses have been employed in the past to print objects such as spark plug insulators. For example, U.S. Pat. No. 2,924,169 issued on Feb. 9, 1960 to Scott, discloses a method and apparatus for printing cylindrical objects such as spark plug insulators including a horizontally disposed, rotating printing wheel which is in rotational and tangential contact with cylindrical engraved plates to transfer an image from the plate to the spark plug insulators.
Silk screening technology has also been employed in the art as evidenced by U.S. Pat. No. 4,640,188 issued on Feb. 3, 1987 to Cosson et al. The Cossan et al '188 patent discloses a silk screen transfer printing apparatus for cylindrical objects including a print transfer drum which is rotatable about horizontal axis. A screen printing head is arranged horizontally above the print transfer drum and is brought down into contact with horizontal pads to transfer an image from the screen printing head to the pads. The drum is then rotated to orientate the pads in a vertical position and the pads brought into contact with the spark plug insulator to transfer the image from the pad to the insulator.
Still another example of the prior art is shown in U.S. Pat. No. 3,685,442 issued on Aug. 22, 1972, to Harwell, Jr. The Harwell, Jr. '442 patent discloses a rotary offset silk screening apparatus with squeegee adjustments wherein a continuous screen defining an image to be printed is mounted within the periphery of a rotary head. Ink is then forced through the screen onto a soft elastomeric rotor positioned for tangential contact with the periphery of the mounted screen. The image picked up by the soft elastomeric roller is transferred to a work piece. The Harwell, Jr. '442 patent also discloses a means for selectively adjusting the position of the squeegee to vary the pressure of the squeegee as it bears against the continuous screen.
However, although the prior art as discussed above accomplishes the objects of those inventions, simplicity is sacrificed in an effort to transfer an image from a print head to the object to be printed. The prior art represents complex apparatus with many moving parts and expensive components. Further, many printers require that the object be indexed from a vertical to a horizontal position to be printed. Then, it is necessary to again index the object to a vertical position. This further complicates the printing process and adds costs to the assemblies. Finally, to the extent the prior art discloses printing apparatuses wherein the object to be printed does not need to be indexed horizontally, those assemblies are awkward and do not result in a clear and precise image on the printed object.